In cooperation with Dr. G. Z. Williams and staff, records of some 30 different biochemical and hematological tests performed serially on several hundred healthy volunteers are being collated to provide a large-scale test of the usefulness of each of 3 stochastic forecasting models described in last year's report. These models together with the general theory of variance components in clinical chemistry, have also been applied to the development of criteria for setting goals of precision and accuracy in laboratory methods, depending on the context of use. Analysis of a 5-month study of weekly serum biochemistries in 37 normal volunteers has been completed and published, providing new data on intra- and inter-individual biological variances. Further work is in progress, utilizing these data, to construct and test theoretical links between population-based reference distributions and individual series of results so as to improve the forecasting accuracy of statistical time series models applied to short series. BIBLIOGRAPHIC REFERENCES: Williams, G.Z., Harris, E.K., and Widdowson, G.M.: Comparison of estimates of long-term analytical variation derived from subject samples and control serum. Clin. Chem., 23, 100-104 (January, 1977). Pickup, J.F., Harris, E.K., Kearns, M., and Brown, S.S.: Intra-individual variation of some serum constituents and its relevance to population-based reference ranges. Clin. Chem. 23, 842-850 (May 1977).